The development of Gutenberg's printing press had a huge impact on the United States as well as around the world. It not only helped produce millions of books at a much faster pace and lowered the cost of them, but also helped spark the Age of Enlightenment and facilitated the spread of new and often controversial ideas.
The electric light also had an incredible impact on the U.S. We always take our electricity for granted but all it takes is one short power outage and people realize how important it really is. Although many inventors worked on the light bulb, it was Thomas Edison and Joseph Swan who patented the first long lasting light bulbs in 1879 and 1880 which liberated society from the their reliance on daylight. Electric lights began being used everywhere from homes to cars to flashlights. This paved way for many new electric appliances to come.
One of the most important innovations EVER are antibiotics. Antibiotics saved millions of lives by killing and preventing the growth of harmful bacteria. A few scientists worked on this as well but it was Alexander Fleming who made the first leap in antibiotics when he accidentally discovered penicillin in 1928. This played a huge role in World War 1 when nearly 20% of soldiers who contracted bacterial pneumonia died, penicillin made that drop to nearly 1%.
I hope this helped you :))